The present invention relates to a nozzle plate for an ink-jet printer and a method for manufacturing the same. More specifically, the present invention relates to a technical field in which a nozzle hole to jet ink is formed so as to penetrate the nozzle plate in the thickness direction thereof and a water-repellent film is formed on an ink downstream-side surface of the both sides of the nozzle plate at which the nozzle hole is opened.
Conventionally, an ink-jet head that jets ink in a pressure chamber from a nozzle is well known, in which there is provided the pressure chamber with ink filled up therein, a nozzle connected to the pressure chamber, and a pressure impressing device, such as a piezoelectric actuator, impressing a pressure to the pressure chamber to jet ink from the nozzle. In general, the nozzle includes a nozzle hole that penetrates a nozzle plate in the thickness direction thereof, and a water-repellent film is formed on an ink downstream-side (ink jetting-side) surface of the both sides (both sides that are opposite to each other in the thickness direction of the nozzle plate) of the nozzle plate at which the nozzle hole is opened. Here, the water-repellent film is provided so that the ink downstream-side surface, especially a portion surrounding the nozzle hole, can be prevented from being wet by the ink, resulting in an excellent maintenance of ink jetting function from the nozzle. That is, if the portion surrounding the nozzle hole is wet by ink, a direction, a speed or amount of jetting ink may be changed according to a degree of how much the ink is wet. Therefore, in order to improve stability and accuracy of printing, it may be necessary that such water-repellent film is formed on the ink downstream-side surface of the nozzle plate.
Meanwhile, the nozzle hole is formed by pressing, as shown for example in Japanese Patent Laid-Open Publication No. 4-299150. In this case, if the water-repellent film is formed before forming the nozzle hole by the press processing, part of the water-repellent film surrounding the nozzle hole may be damaged and worn off by the press processing subsequently applied. That is, the conventional process provides a water-repellent film formed by plating with considerably increased thickness of the film. Therefore, part of water-repellent film surrounding the nozzle hole may be worn off easily by the press processing subsequently applied.
Even if the water-repellent film is formed by other methods than plating, as long as a thickness of the film formed is as considerably big as that by conventional plating, the water-repellent film may be worn off easily during forming the nozzle hole. Further, even other forming process than the press processing, such as electric discharge processing, laser processing or the like, are applied, the water-repellent film with a big thickness thereof may be damaged and worn off easily.
Accordingly, in the conventional process for forming water-repellent film and nozzle hole, forming water-repellent film is done after forming nozzle hole.
However, if forming water-repellent film is done after forming nozzle hole like the conventional process, it should be difficult for part of water-repellent film surrounding the nozzle hole just close to an edge of the hole to be formed uniformly around there. Even if the above process can provide better forming of the water-repellent film, compared to the process in which forming nozzle holes is done after forming water-repellent film, forming water-repellent film after forming nozzle hole with any hole-forming processing should cause a problem that some ink-wet area is formed around the edges of the nozzle holes inevitably. Accordingly, further improvement to reduce this ink-wet area as much as possible for increasing accuracy of printing will be demanded.
In view of the above-described conventional problem, it is an object of the present invention to provide a water-repellent film that is formed as uniformly as possible, extending just close to the edge of the nozzle hole so as to improve accuracy of printing.
In order to achieve the above object, the present invention provides a nozzle plate for an ink-jet printer comprising a nozzle hole to jet ink formed so as to penetrate the nozzle plate in the thickness direction thereof and a water-repellent film formed on an ink downstream-side surface of the both sides of the nozzle plate at which the nozzle hole is opened, wherein a thickness of the water-repellent film is less than 1 xcexcm.
According to the nozzle plate for an ink-jet printer of the present invention, the nozzle hole can be formed after forming the water-repellent film. That is, the thickness of the water-repellent film is so thin that a portion surrounding the nozzle hole can be maintained at a state where a film over the portion is not easy to get damaged and substantially uniform even if the nozzle hole is formed after forming the water-repellent film. Meanwhile, the water-repellent film can be formed easily by Sol-Gel process and a fixing strength of the film on the nozzle plate can be high even if the film is so thin. Accordingly, it can improve a function of the ink jet resulting in increasing accuracy of printing.
Further, it is preferred that the present invention provides a nozzle plate for an ink-jet printer of the above, wherein the nozzle plate is formed so that an area of a portion surrounding the nozzle hole that is wet by ink and formed at the ink downstream-side surface is less than 10% of an opening area of the nozzle hole formed at the ink downstream-side surface when at least the nozzle hole of the nozzle plate is once dipped in ink of a container in such a manner that the ink downstream-side surface thereof is positioned so as to be substantially perpendicular to a surface of ink and then pulled up.
That is, when at least the nozzle hole of the nozzle plate is dipped in ink and then pulled up, the ink is repelled by the water-repellent film resulting in ink dripping away from the surface of the nozzle plate. Accordingly, in general, no portion that is wet by the ink on the surface of the downstream-side surface of the plate may exist. However, it should be difficult to form the water-repellent film uniformly to perfection just over the portion surrounding the nozzle hole. Therefore, the ink-wet portion may exist. However, if the area of the ink-wet portion is less than 10% of the opening area of the nozzle hole formed at the ink downstream-side surface, it can be said that the function of ink jetting is good and the part of water-repellent film surrounding the nozzle hole just close to an edge of the hole is substantially formed uniformly. In other words, if the area of the ink-wet portion is this much, a direction of ink jet can be stable, resulting in suppressing a deviation of ink drops from proper ink-adhered positions in a sub-scanning direction to a certain degree (less than 4 xcexcm) in which little lateral lines or the like is printed. Further, a speed of ink jet can also be stabilized, so that the deviation of the ink drops from proper ink-adhered positions in a main-scanning direction can be suppressed.
Further, it is preferred that the present invention provides a method for manufacturing a nozzle plate for an ink-jet printer, in which firstly a water-repellent film is formed and then a nozzle hole is formed.
Specifically, that is a method for manufacturing a nozzle plate for an ink-jet printer, in which the nozzle plate includes a nozzle hole to jet ink formed so as to penetrate the nozzle plate in the thickness direction thereof and a water-repellent film formed on an ink downstream-side surface of the both sides of the nozzle plate at which the nozzle hole is opened, the method comprising the steps of forming the water-repellent film on one surface of the both sides of a plate material by Sol-Gel process and forming the nozzle hole so as to penetrate the plate material in the thickness direction thereof after forming the water-repellent film.
According to the method for manufacturing a nozzle plate for an ink-jet printer of the present invention, it can be easy to make the water-repellent film considerably thin and the water-repellent film with a high fixing strength on the nozzle plate can be provided even if the film is considerably thin. Therefore, even if the nozzle hole is formed after forming the water-repellent film, the portion of the water-repellent film surrounding the nozzle hole can be formed uniformly so that it should not be easy to get damaged. Accordingly, it can improve the function of the ink jet resulting in increasing accuracy of printing.
Further, it is preferred that a thickness of the water-repellent film formed in the above step of forming the water-repellent film is less than 1 xcexcm.
According to this, it can improve the function of the ink jet certainly, as described above.
Further, it is preferred that the above step of forming the nozzle hole is a step of forming the nozzle hole by applying electric discharge processing or laser processing.
According to this, a portion of the water-repellent film surrounding the nozzle hole can be formed more uniformly, compared to the nozzle hole formed by pressing.